1. Field of the Invention
The present invention relates generally to window blinds of the type operated by lift cords and made of flexible window covering material such as a roman shade or pleated shade.
2. Description of the Related Art
Various vertical window blinds including venetian blinds, roller shades, roman shades, and the like are known. These window blinds commonly comprise a headrail, a bottom rail and a window covering material extending between them. Lift cords extend from the bottom rail into the headrail for raising and lowering the blind. The window covering material may be pleated or cellular material, woven woods or grasses or roman shade material that is raised and lowered or slats on ladders that can be raised and lowered as well as tilted for light control.
A venetian blind provides the widest range of light control. The slats can be raised to a fully open position, lowered to cover the entire window and tilted vertically to a fully closed position or lowered to a fully lowered or partially lowered position with the slats tilted at a selected orientation between vertical and horizontal. Roman, pleated and cellular shades have a softer appearance than venetian blinds. However, a conventional roman shade and other fabric shades can only be raised and lowered to cover all or a portion of the window. When a roman shade is in a fully lowered or partially lowered position, it cannot be controlled or adjusted to change the amount of light transmittance as occurs when one tilts the slats in a fully lowered or partially lowered venetian blind.
Although the slats in most venetian blinds are wood, aluminum or plastic, it is known to make fabric slats. One example of a fabric slat is disclosed in U.S. Pat. No. 5,829,506 to Zorbas. Like wood, aluminum and plastic slats fabric slats are hung on ladders or attached to ladder rungs and may have transverse stiffeners. Venetian blinds having fabric slats operate in the same manner as venetian blinds having wood, aluminum or plastic slats.